Toolholder assembly for machine tool

ABSTRACT

In a device for feeding a quill of machine tool, which is slidable axially in a support, the quill is threaded externally and cooperates with a lead nut rotatable concentrically with respect to the quill and is integral with a gear rotatable to effect the advance of the quill. The lead nut comprises two parts which are spaced axially by a flexible annular plate formed between an internal groove and an adjacent external groove in the lead nut to permit axial adjustment of the two parts. The lead nut includes two independent ball circulation circuits one for each one of the two parts respectively. The quill is mounted in the support by means of two elastic bushes spaced from one another and adjustable axially by means of a pressure collar to eliminate axial play of the quill.

White States Patent Fantoni 1 Feb. 8, 1972 [54] TOOLHOLDER ASSEMBLY FOR2,791,922 /1957 Robinson ..77/34.4 MACHINE TOOL 3,369,422 2/1968 Sears74/424.8 R 3,479,897 11/1969 Holthofer ..74/441 [72] inventor: GiuseppeFantom, lvrea, ltaly Prima Examiner-Leonard H. Gerin 73A=1.c.o11m&c.s...1 sslgnee Italy ye p A "ea Attorney-Birch, Swindler,McKie & Beckett [22] Filed: Mar. 2, 1970 [57] 4 ABSTRACT [21] App]. No.:15,491 In a device for feeding a quill of machine tool, which isslidable axially in a support, the quill is threaded externally andcooperates with a lead nut rotatable concentrically with ForeignApplication Pnonty Dam respect to the quill and is integral with a gearrotatable to ef- Mar. 3, 1969 Italy ..5082() A/69 e the advance of thequill- The lead m1! comprises two Parts which are spaced axially by aflexible annular plate formed 52 us. Cl. ..74/424.s R, 74/441 between aninternal groove and adjacent external groove in 51 1m. (:1 ..F16h 1/18,F1611 55/18 the e to Fermit axial adjustment of the P The 581 Field 01Search ..74 424.s R, 441 424.8 A lead includes We!ndent cimlatio"circuit one for each one of the two parts respectively. The quill ismounted in the support by means of two elastic bushes spaced [56]References Cited from one another and adjustable axially by means of apres- UNlTED STATES PATENTS sure collar to eliminate axial play of thequill.

2,869,403 1/1959 Bent ..74/424.8 R X 7 Claims, 2 Drawing Figures j g M 1\g yg 4 n 1 P V as " /LA [5 E10 8 1s 14 ems E3 E- 17 5 36 34 24 27 51 54?) 25 Q 28 g 22 19 4 23 2 1 8 T 60 57-E 59 2 21 61 I E 154 1 z 5 56";53 4 E PATENTED FEB 8 I972 INVENTOR GIUSEPPE FANTON' TOOLHOLDER ASSEMBLYFOR MACHINE TOOL BACKGROUND OF THE INVENTION 1. Field of the inventionThe present invention relates to a toolholder assembly with an operatingdevice for feeding a spindle holder for a machine tool wherein thespindle is adapted to house a tool and is rotatable in the holder.

2. Description of the prior art In machine tools, the spindle holder isnormally caused to advance by means of a pinion meshing with a rackfixed to, or integral with, the holder. The pinion is thereforesubjected to a heavy pressure which is applied eccentrically withrespect to the holder.

An operating device for feeding a holder has also been proposed in whichthe holder, fixed by means of a collar and a sleeve to a lead screwcooperating with a screw arranged parallel thereto, is alongside thespindle. This operating device has the disadvantage that the axialthrust is not located on the axis of movement and, therefore, the screwis subjected to bending stresses which tend to damage the screw itselfand the holder. All the known devices moreover require complicatedsystems for eliminating backlash.

SUMMARY OF THE INVENTION These drawbacks are obviated by the presentinvention, which provides a toolholder assembly with an operating devicefor feeding a spindle holder for a machine tool, wherein the spindle isadapted to house a tool and is rotatable in the spindle holder, which isin turn slidable axially in a support, the spindle holder being threadedexternally and cooperating with a lead nut rotatable concentrically withrespect to the spindle holder in the support, a gear integral with thelead nut being adapted to rotate to efi'ect the advance of the spindleholder.

Preferably the lead nut is of the ball circulation type and includes twoindependent circulation circuits disposed in two axially spaced parts ofthe lead nut, the lead nut having between these parts an internal grooveand an adjacent external groove, a thin flexible annular plate remainingbetween the grooves for permitting axial adjustment of the two partsrelative to each other.

The following description of a preferred embodiment of the invention isgiven by way of example, with the aid of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section of anassembly embodying the invention;

FIG. 2 is a section on the line II-II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, thetoolholder assembly includes a spindle 4 in which a tool 5 can be fixed.The spindle 4 is rotatable in two ball bearings 6 and 7 in a holder 8slidable axially in a support 9 for the spindle head. The ball bearing 6is held against a shoulder 10 of the spindle 4 by a ring 11 driven coldon to a portion 12 of the spindle 4. The bearing 7 is held against ashoulder 13 of the spindle 4 by two thrust bearings 14 and 15 forcedtowards the shoulder 13 by means of a ring 16 driven cold on to anotherportion 17 of the spindle 4. A spacer 18 housed in the holder 3 isinterposed between the bearings 6 and 14.

The holder 8 is guided in the support 9 by means of two adjustableelastic bushes l9 and 20. The bush I9 is arranged in the support 9 incontact with a ring 21 which abuts against a thrust bearing 22. A spacer23 is interposed between the bush l9 and the bush 20, which latter isheld by a flange 24 fixed to the end of the support 9 by means of fourscrews 25. The pressure exerted by means of the screws 25 compresses theelastic bushes l9 and axially, thus expanding them radially andeliminating radial play between the holder 8 and the bushes themselves.

The rotation of the spindle 4 is produced by a shaft 26 rotatable in twoball bearings 27 and 28 mounted in the support 9, this shaft beingconnected to a motor not shown in the drawing. On the shaft 26 there isfixed a gear 29 in mesh with a pinion 30 integral with a sleeve 31. Thissleeve is rotatable in two ball bearings 32 and 33 mounted in thesupport 9 and is integral with an internally splined portion 34 whichengages with a splined tail portion 35 of the spindle 4.

The holder 8 is externally cylindrical and has for a certain length athread 36 the groove of which can cooperate with a series of balls 37circulating in a lead nut 38. This lead nut is rotatable within thesupport 9 between two thrust bearings 22 and 39. The lead nut 38comprises two parts 40 and 41 which are spaced axially and providedinternally with two corresponding threads 42 and 43 of equal pitch butseparated from each other. The beginning and the end of each of thethreads 42 and 43 are connected by two separate circulation circuits,only one of which can be seen in FIG. 2. Each of these circuitscomprises two radial passages 44 and 45 and a helical passage 46 whichare formed in the body of the lead nut 38 and closed by a sleeve 47embracing the lead nut 38.

Between the two parts 40 and 41, the lead nut 38 is moreover providedwith an external groove 48 (FIG. I) and an internal groove 49. A thinannular plate 50 is left between the grooves and is flexible forpermitting relative axial adjustment of the two threads 42 and 43. Forthis adjustment there are provided four screws 51, which are screwedinto the part 40 of the lead nut 38 through the part 41 and an equalnumber of holes in the plate 50. Another four screws 52 can be screwedinto the part 40 so as to bear against the side of the part 41.

During the fitting of the holder, the adjustment for preloading theballs 37 and eliminating backlash between the screw 36 and the lead nut38 is effected by first screwing in the screws 51 so as to bend theplate 50 until any play present between the lead nut 38 and the screw 36of the holder 8 is eliminated. The screws 52 are then screwed in untiltheir ends press on the part 51 against the side of the groove 49. Inthis way, the screws 51 are prevented from slackening or tighteningbecause of vibration.

The feed and return of the holder are operated through the medium of ashaft 53 rotatable in two ball bearings 54 and 55 mounted in the support9, the shaft being adapted to be rotated by an electric motor not shownin the drawing. A gear 56 fixed on the shaft 53 is in mesh with a gear57 fast with a second shaft 58 rotatable in two ball bearings 59 and 60.Another gear 61 fixed to the shaft 58 meshes with a ring gear 62integral with the lead nut 38.

It is therefore clear that the holder 8 is threaded externally andcooperates with a lead nut 38 rotatable concentrically with respect tothe holder 8 in the fixed support 9 of the working head and that thegear 62 integral with the lead nut 38 is rotated to produce the feed ofthe holder, so that the action of the lead nut 38 is centered on theaxis of the holder itself.

What I claim is:

1. An operating device for feeding a nonrotatable spindle holder of amachine tool including a frame, a spindle rotatable in said spindleholder and adapted to support a tool, and means for mounting saidspindle holder slidable axially in said frame, the combinationcomprising:

a threaded portion on the external surface of said spindle holder,

a lead nut rotatable on said frame concentric with said spindle holderand cooperating with said threaded portion,

a gear concentrically bodily rotatable with said lead nut, rotation ofsaid gear and said lead nut axially feeding said spindle holder, and

means for rotating said gear and said lead nut independently of saidspindle.

2. A device according to claim 1, further including:

elastic bushings for mounting said spindle holder on said frame, saidbushing being axially spaced from one another, and

a pressure collar engaging one of said bushings and adjustable axiallyto eliminate axial play of said spindle holder in said frame.

3. A device according to claim 1, wherein said lead nut is formed intotwo axially spaced portions;

by an internal groove on said lead nut, and an external groove on saidlead nut adjacent to said internal groove, said grooves being locatedbetween said two portions; and

said device including a flexible annular plate fonned between saidgrooves to join said portions and to permit axial adjustment of said twoparts relative to each other.

4. A device according to claim 3, wherein said lead nut is of the ballcirculation type, and includes:

two independent circulation circuits, the balls of said circuits beingdisposed in one of said two portions.

5. The device according to claim 4 further including:

elastic bushings for mounting said spindle holder on said frame, saidbushing being axially spaced from one another, and

a pressure collar engaging one of said bushings and adjustable axiallyto eliminate axial play of said spindle holder in said frame,

6. A device according to claim 3, comprising:

at least one first screw crossing one of said portions and said plateand screwed on the other of said portions to effect adjustment byaxially flexing said plate, and

at least one other screw also screwed on said other part and crossingsaid plate to bear against said one part to prevent slackening andtightening of said first screw.

7. The device according to claim 1 further including a splined portionintegral with said spindle;

a drive member, rotatably supported in said frame;

said drive member having an aperture configured congruent with saidsplined portion and slidably receiving said splined portion so thatrotation of said drive member effects rotation of said spindle whilepermitting axial movement of said spindle with respect to said frame.

1. An operating device for feeding a nonrotatable spindle holder of amachine tool including a frame, a spindle rotatable in said spindleholder and adapted to support a tool, and means for mounting saidspindle holder slidable axially in said frame, the combinationcomprising: a threaded portion on the external surface of said spindleholder, a lead nut rotatable on said frame concentric with said spindleholder and cooperating with said threaded portion, a gear concentricallybodily rotatable with said lead nut, rotation of said gear and said leadnut axially feeding said spindle holder, and means for rotating saidgear and said lead nut independently of said spindle.
 2. A deviceaccording to claim 1, further including: elastic bushings for mountingsaid spindle holder on said frame, said bushing being axially spacedfrom one another, and a pressure collar engaging one of said bushingsand adjustable axially to eliminate axial play of said spindle holder insaid frame.
 3. A device according to claim 1, wherein said lead nut isformed into two axially spaced portions; by an internal groove on saidlead nut, and an external groove on said lead nut adjacent to saidinternal groove, said grooves being located between said two portions;and said device including a flexible annular plate formed between saidgrooves to join said portions and to permit axial adjustment of said twoparts relative to each other.
 4. A device according to claim 3, whereinsaid lead nut is of the ball circulation type, and includes: twoindependent circulation circuits, the balls of said circuits beingdisposed in one of said two portions.
 5. The device according to claim 4further including: elastic bushings for mounting said spindle holder onsaid frame, said bushing being axially spaced from one another, and apressure collar engaging one of said bushings and adjustable axially toeliminate axial play of said spindle holder in said frame.
 6. A deviceaccording to claim 3, comprising: at least one first screw crossing oneof said portions and said plate and screwed on the other of saidportions to effect adjustment by axially flexing said plate, and atleast one other screw also screwed on said other part and crossing saidplate to bear against said one part to prevent slackening and tighteningof said first screw.
 7. The device according to claim 1 furtherincluding a splined portion integral with said spindle; a drive member,rotatably supported in said frame; said drive member having an apertureconfigured congruent with said splined portion and slidably receivingsaid splined portion so that rotation of said drive member effectsrotation of said spindle while permitting axial movement of said spindlewith respect to said frame.